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+'\"
+'\" Copyright (c) 2007 Donal K. Fellows
+'\"
+'\" See the file "license.terms" for information on usage and redistribution
+'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+'\"
+.so man.macros
+.TH define n 0.3 TclOO "TclOO Commands"
+.BS
+'\" Note: do not modify the .SH NAME line immediately below!
+.SH NAME
+oo::define, oo::objdefine \- define and configure classes and objects
+.SH SYNOPSIS
+.nf
+package require TclOO
+
+\fBoo::define\fI class defScript\fR
+\fBoo::define\fI class subcommand arg\fR ?\fIarg ...\fR?
+\fBoo::objdefine\fI object defScript\fR
+\fBoo::objdefine\fI object subcommand arg\fR ?\fIarg ...\fR?
+.fi
+.BE
+
+.SH DESCRIPTION
+The \fBoo::define\fR command is used to control the configuration of classes,
+and the \fBoo::objdefine\fR command is used to control the configuration of
+objects (including classes as instance objects), with the configuration being
+applied to the entity named in the \fIclass\fR or the \fIobject\fR argument.
+Configuring a class also updates the
+configuration of all subclasses of the class and all objects that are
+instances of that class or which mix it in (as modified by any per-instance
+configuration). The way in which the configuration is done is controlled by
+either the \fIdefScript\fR argument or by the \fIsubcommand\fR and following
+\fIarg\fR arguments; when the second is present, it is exactly as if all the
+arguments from \fIsubcommand\fR onwards are made into a list and that list is
+used as the \fIdefScript\fR argument.
+.SS "CONFIGURING CLASSES"
+.PP
+The following commands are supported in the \fIdefScript\fR for
+\fBoo::define\fR, each of which may also be used in the \fIsubcommand\fR form:
+.TP
+\fBconstructor\fI argList bodyScript\fR
+.
+This creates or updates the constructor for a class. The formal arguments to
+the constructor (defined using the same format as for the Tcl \fBproc\fR
+command) will be \fIargList\fR, and the body of the constructor will be
+\fIbodyScript\fR. When the body of the constructor is evaluated, the current
+namespace of the constructor will be a namespace that is unique to the object
+being constructed. Within the constructor, the \fBnext\fR command should be
+used to call the superclasses' constructors. If \fIbodyScript\fR is the empty
+string, the constructor will be deleted.
+.TP
+\fBdeletemethod\fI name\fR ?\fIname ...\fR
+.
+This deletes each of the methods called \fIname\fR from a class. The methods
+must have previously existed in that class. Does not affect the superclasses
+of the class, nor does it affect the subclasses or instances of the class
+(except when they have a call chain through the class being modified).
+.TP
+\fBdestructor\fI bodyScript\fR
+.
+This creates or updates the destructor for a class. Destructors take no
+arguments, and the body of the destructor will be \fIbodyScript\fR. The
+destructor is called when objects of the class are deleted, and when called
+will have the object's unique namespace as the current namespace. Destructors
+should use the \fBnext\fR command to call the superclasses' destructors. Note
+that destructors are not called in all situations (e.g. if the interpreter is
+destroyed). If \fIbodyScript\fR is the empty string, the destructor will be
+deleted.
+.RS
+Note that errors during the evaluation of a destructor \fIare not returned\fR
+to the code that causes the destruction of an object. Instead, they are passed
+to the currently-defined \fBbgerror\fR handler.
+.RE
+.TP
+\fBexport\fI name \fR?\fIname ...\fR?
+.
+This arranges for each of the named methods, \fIname\fR, to be exported
+(i.e. usable outside an instance through the instance object's command) by the
+class being defined. Note that the methods themselves may be actually defined
+by a superclass; subclass exports override superclass visibility, and may in
+turn be overridden by instances.
+.TP
+\fBfilter\fR ?\fI\-slotOperation\fR? ?\fImethodName ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below)
+.VE
+sets or updates the list of method names that are used to guard whether
+method call to instances of the class may be called and what the method's
+results are. Each \fImethodName\fR names a single filtering method (which may
+be exposed or not exposed); it is not an error for a non-existent method to be
+named since they may be defined by subclasses.
+.VS
+By default, this slot works by appending.
+.VE
+.TP
+\fBforward\fI name cmdName \fR?\fIarg ...\fR?
+.
+This creates or updates a forwarded method called \fIname\fR. The method is
+defined be forwarded to the command called \fIcmdName\fR, with additional
+arguments, \fIarg\fR etc., added before those arguments specified by the
+caller of the method. The \fIcmdName\fR will always be resolved using the
+rules of the invoking objects' namespaces, i.e., when \fIcmdName\fR is not
+fully-qualified, the command will be searched for in each object's namespace,
+using the instances' namespace's path, or by looking in the global namespace.
+The method will be exported if \fIname\fR starts with a lower-case letter, and
+non-exported otherwise.
+.TP
+\fBmethod\fI name argList bodyScript\fR
+.
+This creates or updates a method that is implemented as a procedure-like
+script. The name of the method is \fIname\fR, the formal arguments to the
+method (defined using the same format as for the Tcl \fBproc\fR command) will
+be \fIargList\fR, and the body of the method will be \fIbodyScript\fR. When
+the body of the method is evaluated, the current namespace of the method will
+be a namespace that is unique to the current object. The method will be
+exported if \fIname\fR starts with a lower-case letter, and non-exported
+otherwise; this behavior can be overridden via \fBexport\fR and
+\fBunexport\fR.
+.TP
+\fBmixin\fR ?\fI\-slotOperation\fR? ?\fIclassName ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below)
+.VE
+sets or updates the list of additional classes that are to be mixed into
+all the instances of the class being defined. Each \fIclassName\fR argument
+names a single class that is to be mixed in.
+.VS
+By default, this slot works by replacement.
+.VE
+.TP
+\fBrenamemethod\fI fromName toName\fR
+.
+This renames the method called \fIfromName\fR in a class to \fItoName\fR. The
+method must have previously existed in the class, and \fItoName\fR must not
+previously refer to a method in that class. Does not affect the superclasses
+of the class, nor does it affect the subclasses or instances of the class
+(except when they have a call chain through the class being modified). Does
+not change the export status of the method; if it was exported before, it will
+be afterwards.
+.TP
+\fBself\fI subcommand arg ...\fR
+.TP
+\fBself\fI script\fR
+.
+This command is equivalent to calling \fBoo::objdefine\fR on the class being
+defined (see \fBCONFIGURING OBJECTS\fR below for a description of the
+supported values of \fIsubcommand\fR). It follows the same general pattern of
+argument handling as the \fBoo::define\fR and \fBoo::objdefine\fR commands,
+and
+.QW "\fBoo::define \fIcls \fBself \fIsubcommand ...\fR"
+operates identically to
+.QW "\fBoo::objdefine \fIcls subcommand ...\fR" .
+.TP
+\fBsuperclass\fR ?\fI\-slotOperation\fR? ?\fIclassName ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below)
+.VE
+allows the alteration of the superclasses of the class being defined.
+Each \fIclassName\fR argument names one class that is to be a superclass of
+the defined class. Note that objects must not be changed from being classes to
+being non-classes or vice-versa, that an empty parent class is equivalent to
+\fBoo::object\fR, and that the parent classes of \fBoo::object\fR and
+\fBoo::class\fR may not be modified.
+.VS
+By default, this slot works by replacement.
+.VE
+.TP
+\fBunexport\fI name \fR?\fIname ...\fR?
+.
+This arranges for each of the named methods, \fIname\fR, to be not exported
+(i.e. not usable outside the instance through the instance object's command,
+but instead just through the \fBmy\fR command visible in each object's
+context) by the class being defined. Note that the methods themselves may be
+actually defined by a superclass; subclass unexports override superclass
+visibility, and may be overridden by instance unexports.
+.TP
+\fBvariable\fR ?\fI\-slotOperation\fR? ?\fIname ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below) arranges for each of the named
+variables to be automatically made
+available in the methods, constructor and destructor declared by the class
+being defined. Each variable name must not have any namespace
+separators and must not look like an array access. All variables will be
+actually present in the instance object on which the method is executed. Note
+that the variable lists declared by a superclass or subclass are completely
+disjoint, as are variable lists declared by instances; the list of variable
+names is just for methods (and constructors and destructors) declared by this
+class. By default, this slot works by appending.
+.VE
+.SS "CONFIGURING OBJECTS"
+.PP
+The following commands are supported in the \fIdefScript\fR for
+\fBoo::objdefine\fR, each of which may also be used in the \fIsubcommand\fR
+form:
+.TP
+\fBclass\fI className\fR
+.
+This allows the class of an object to be changed after creation. Note that the
+class's constructors are not called when this is done, and so the object may
+well be in an inconsistent state unless additional configuration work is done.
+.TP
+\fBdeletemethod\fI name\fR ?\fIname ...\fR
+.
+This deletes each of the methods called \fIname\fR from an object. The methods
+must have previously existed in that object. Does not affect the classes that
+the object is an instance of.
+.TP
+\fBexport\fI name \fR?\fIname ...\fR?
+.
+This arranges for each of the named methods, \fIname\fR, to be exported
+(i.e. usable outside the object through the object's command) by the object
+being defined. Note that the methods themselves may be actually defined by a
+class or superclass; object exports override class visibility.
+.TP
+\fBfilter\fR ?\fI\-slotOperation\fR? ?\fImethodName ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below)
+.VE
+sets or updates the list of method names that are used to guard whether a
+method call to the object may be called and what the method's results are.
+Each \fImethodName\fR names a single filtering method (which may be exposed or
+not exposed); it is not an error for a non-existent method to be named. Note
+that the actual list of filters also depends on the filters set upon any
+classes that the object is an instance of.
+.VS
+By default, this slot works by appending.
+.VE
+.TP
+\fBforward\fI name cmdName \fR?\fIarg ...\fR?
+.
+This creates or updates a forwarded object method called \fIname\fR. The
+method is defined be forwarded to the command called \fIcmdName\fR, with
+additional arguments, \fIarg\fR etc., added before those arguments specified
+by the caller of the method. Forwarded methods should be deleted using the
+\fBmethod\fR subcommand. The method will be exported if \fIname\fR starts with
+a lower-case letter, and non-exported otherwise.
+.TP
+\fBmethod\fI name argList bodyScript\fR
+.
+This creates, updates or deletes an object method. The name of the method is
+\fIname\fR, the formal arguments to the method (defined using the same format
+as for the Tcl \fBproc\fR command) will be \fIargList\fR, and the body of the
+method will be \fIbodyScript\fR. When the body of the method is evaluated, the
+current namespace of the method will be a namespace that is unique to the
+object. The method will be exported if \fIname\fR starts with a lower-case
+letter, and non-exported otherwise.
+.TP
+\fBmixin\fR ?\fI\-slotOperation\fR? ?\fIclassName ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below)
+.VE
+sets or updates a per-object list of additional classes that are to be
+mixed into the object. Each argument, \fIclassName\fR, names a single class
+that is to be mixed in.
+.VS
+By default, this slot works by replacement.
+.VE
+.TP
+\fBrenamemethod\fI fromName toName\fR
+.
+This renames the method called \fIfromName\fR in an object to \fItoName\fR.
+The method must have previously existed in the object, and \fItoName\fR must
+not previously refer to a method in that object. Does not affect the classes
+that the object is an instance of. Does not change the export status of the
+method; if it was exported before, it will be afterwards.
+.TP
+\fBunexport\fI name \fR?\fIname ...\fR?
+.
+This arranges for each of the named methods, \fIname\fR, to be not exported
+(i.e. not usable outside the object through the object's command, but instead
+just through the \fBmy\fR command visible in the object's context) by the
+object being defined. Note that the methods themselves may be actually defined
+by a class; instance unexports override class visibility.
+.TP
+\fBvariable\fR ?\fI\-slotOperation\fR? ?\fIname ...\fR?
+.VS
+This slot (see \fBSLOTTED DEFINITIONS\fR below) arranges for each of the named
+variables to be automatically made available in the methods declared by the
+object being defined. Each variable name must not have any namespace
+separators and must not look like an array access. All variables will be
+actually present in the object on which the method is executed. Note that the
+variable lists declared by the classes and mixins of which the object is an
+instance are completely disjoint; the list of variable names is just for
+methods declared by this object. By default, this slot works by appending.
+.SH "SLOTTED DEFINITIONS"
+Some of the configurable definitions of a class or object are \fIslotted
+definitions\fR. This means that the configuration is implemented by a slot
+object, that is an instance of the class \fBoo::Slot\fR, which manages a list
+of values (class names, variable names, etc.) that comprises the contents of
+the slot. The class defines three operations (as methods) that may be done on
+the slot:
+.VE
+.TP
+\fIslot\fR \fB\-append\fR ?\fImember ...\fR?
+.VS
+This appends the given \fImember\fR elements to the slot definition.
+.VE
+.TP
+\fIslot\fR \fB\-clear\fR
+.VS
+This sets the slot definition to the empty list.
+.VE
+.TP
+\fIslot\fR \fB\-set\fR ?\fImember ...\fR?
+.VS
+This replaces the slot definition with the given \fImember\fR elements.
+.PP
+A consequence of this is that any use of a slot's default operation where the
+first member argument begins with a hyphen will be an error. One of the above
+operations should be used explicitly in those circumstances.
+.SS "SLOT IMPLEMENTATION"
+Internally, slot objects also define a method \fB\-\-default\-operation\fR
+which is forwarded to the default operation of the slot (thus, for the class
+.QW \fBvariable\fR
+slot, this is forwarded to
+.QW "\fBmy \-append\fR" ),
+and these methods which provide the implementation interface:
+.VE
+.TP
+\fIslot\fR \fBGet\fR
+.VS
+Returns a list that is the current contents of the slot. This method must
+always be called from a stack frame created by a call to \fBoo::define\fR or
+\fBoo::objdefine\fR.
+.VE
+.TP
+\fIslot\fR \fBSet \fIelementList\fR
+.VS
+Sets the contents of the slot to the list \fIelementList\fR and returns the
+empty string. This method must always be called from a stack frame created by
+a call to \fBoo::define\fR or \fBoo::objdefine\fR.
+.PP
+The implementation of these methods is slot-dependent (and responsible for
+accessing the correct part of the class or object definition). Slots also have
+an unknown method handler to tie all these pieces together, and they hide
+their \fBdestroy\fR method so that it is not invoked inadvertently. It is
+\fIrecommended\fR that any user changes to the slot mechanism be restricted to
+defining new operations whose names start with a hyphen.
+.VE
+.SH EXAMPLES
+This example demonstrates how to use both forms of the \fBoo::define\fR and
+\fBoo::objdefine\fR commands (they work in the same way), as well as
+illustrating four of the subcommands of them.
+.PP
+.CS
+oo::class create c
+c create o
+\fBoo::define\fR c \fBmethod\fR foo {} {
+ puts "world"
+}
+\fBoo::objdefine\fR o {
+ \fBmethod\fR bar {} {
+ my Foo "hello "
+ my foo
+ }
+ \fBforward\fR Foo ::puts -nonewline
+ \fBunexport\fR foo
+}
+o bar \fI\(-> prints "hello world"\fR
+o foo \fI\(-> error "unknown method foo"\fR
+o Foo Bar \fI\(-> error "unknown method Foo"\fR
+\fBoo::objdefine\fR o \fBrenamemethod\fR bar lollipop
+o lollipop \fI\(-> prints "hello world"\fR
+.CE
+.PP
+This example shows how additional classes can be mixed into an object. It also
+shows how \fBmixin\fR is a slot that supports appending:
+.PP
+.CS
+oo::object create inst
+inst m1 \fI\(-> error "unknown method m1"\fR
+inst m2 \fI\(-> error "unknown method m2"\fR
+
+oo::class create A {
+ \fBmethod\fR m1 {} {
+ puts "red brick"
+ }
+}
+\fBoo::objdefine\fR inst {
+ \fBmixin\fR A
+}
+inst m1 \fI\(-> prints "red brick"\fR
+inst m2 \fI\(-> error "unknown method m2"\fR
+
+oo::class create B {
+ \fBmethod\fR m2 {} {
+ puts "blue brick"
+ }
+}
+\fBoo::objdefine\fR inst {
+ \fBmixin -append\fR B
+}
+inst m1 \fI\(-> prints "red brick"\fR
+inst m2 \fI\(-> prints "blue brick"\fR
+.CE
+.SH "SEE ALSO"
+next(n), oo::class(n), oo::object(n)
+.SH KEYWORDS
+class, definition, method, object, slot
+.\" Local variables:
+.\" mode: nroff
+.\" fill-column: 78
+.\" End: